1. Field of the Invention
The invention relates to a Marx generator incorporating a low-cost circuit structure possessing charging and decoupling resistors having long-term resistances to high voltages.
The impulse-voltage generator discovered by Professor Marx (Braunschweig TU) in 1923 is used to produce a high-voltage pulse, for example for insulation-testing purposes, to investigate the behavior of gases in strong electrical fields or, according to DE 101 51 565 A1, to stimulate a resonator to emit high-power microwave energy.
2. Discussion of the Prior Art
The basic function of the Marx generator is based on a capacitor bank having a number n (n=1, 2, 3, . . . , i) of capacitors connected in parallel with one another being charged to a reasonably high input voltage, which is produced by a DC voltage source via an electronic voltage converter, and then being connected in series so that n-times the input voltage is available as the output voltage across this series circuit. In this case, the change from parallel connection to series connection of in each case two successive capacitors in the capacitor bank is carried out by means of a spark gap. When a first of these spark gaps is triggered, then all of the other spark gaps of the capacitor bank ignite virtually at the same time. The response of the first spark gap can be predetermined by means of its response voltage, that is to say by means of the cross-section geometry and the distance between the spark-gap electrodes; alternatively, the response of the first of the spark gaps is initiated by a trigger pulse supplied to it externally. Decoupling resistors, which also act as charging resistors that govern the time constants, prevent one of the two capacitors, between which the spark gap in order to connect them in series is located, being short-circuited as a result of the ignition of the spark gap. In consequence, the series connection of the charging and decoupling resistors when the capacitors are changed to be connected in series acts as a high-voltage voltage divider. High-voltage-resistant resistors must therefore be used in this case, as well, although these are expensive, and their electrical characteristics frequently change in practice, over the course of a lengthy sequence of operating cycles of the Marx generator. This results in the Marx generator not operating in a stable manner over a lengthy time period if it is intended to operate the microwave resonator that has been mentioned virtually quasi-continuously. The withstand voltages of the resistors could admittedly be derated, but this would increase the costs even further and would nevertheless not ensure long-term stable operation.
The present invention is therefore based on the technical problem of using low-cost circuit means to produce a Marx generator whose charging and decoupling resistors have long-term resistance to high voltages.